Electrode structure



Sept. 4, 1945. c. H. LARsoN ELECTRODE STRUCTURE 2 Sheets-Sheet 1 Filed April 19, 1941 ggg;

Cad/Lamar? Y BYZ;

sept', 4, 1945. c. H. LARsoN 2,384,423

ELEbTRoDE STRUCTURE Filed April 19, 1941 zsheetsfsheet 2 INVENT OR.

Caf'/J E Lason BY M Patented Sept. 4, 1945 Y. Carl H. vLarson, Elkhart, Ind., Y y A' Adlake Company, a corpor .Application April 1.9, 1941 v 2 claims. (Cisca-112) i My invention relates to mercury switchesfand more particularly toan improved electrode structurefor use in such devices. i

In mercury switches,A two electrodes and a body of mercury are ordinarily provided within. a sealed envelope; onek of the electrodes being disposed within the envelope'in such manner as to' be intermittently immersed bythe mercury and thereby complete-thecircuit through the electrodes. 1 To prevent premature destruction of the intermittently immersed electrode, a ycup is' provided withinthe envelope to retain a small quantity; of mercury in continuous .contact with thel intermittently immersed electrode so that any arcing, which occurs in. making or breaking the circuit through the electrodes, will occur between two bodies of mercury. While this arrangement' is satisfactory difliculty .has been experienced in mounting the electrodecup within the switch.

Thererare broadlythree methods of mounting theelectrode cup, namely, by fusing the electrode cupto aglass electrode sleeve, by 'the use of cement, or bymechanical means. A fusedbond has proved satisfactory,A but isslow and expensive to form and the choice oft-,ceramic material which4 may be usedtoform thecup is limitedas the material must have substantially ythe same coliiicientof thermalexpansion as the'glass in ,or'- der. to prevent cracking ofthe fused portion with temperature changes.; eral, `"unsatisfactory asthey are subject to unexpected failure andleakage, and tend to introduce objectionable impurities into the mercury jand the gas lill., Mechanicall means heretoforeemployed have, in general, been objectionablegeither becausethe cupl hasvnot been held rmly in position, ory because the breakage of the Y fragile ceramic material during assembly has been excessive'. In substantially all cases, however, where the cup is firmly -held .in place, some one or more walls rof the cup has been formed with an openadapted to be subsequently sealed by fusion, cement, or other means. This sealed opening is a point 'of potential leakage, and is, therefore, ob-

Amongl th'e objects of my invention are the provision of improved and simplified means whereby ran integrally formed ceramicy cup` havlmperforate walls may be attached to aswitch electrode ,withouty regard tothe coemcient oi?v thermal'expansion of either material, which will provide a strong trouble-free bond, which may bey Leasily, formed and, attached without danger of ',lireakage",Y Awhich kmay be attached V directly to efrilicltfd? #idyllic-Pieces ,not mplowment Cementbonds are,fin;gen

l level of the mercury fill. rThe electrodes I8 and.

Mien, culling, f.,

f These arid: other ,objects wcuifbeegiae aparentf ciflcationg and d from y' the mmh@ .folwwii s drawings;u in'which' Y Fig. 1 is a vertical sectionalview of la displacer type mercury switch illustrating 'one embodiment ofmyinventi'on; .Y fj Fig. 2 is avertical sectional view of adisplacer type mercury switch illustrating a modification of the embodiment shown in Figli; f A

Fig. 3 is a vertical sectional view of a displacer` type mercury's'witch illustrating a modified form' of my device incorporating a time delay element;` Fig. 4 is avertical'sectional view of kafdisplacer type mercury switch illustrating another vembodiment of my invention;

Fig. 5 is anv isometric; view structure illustrated in Fig. -fl; y n

Fig; 16 is a vertical sectional view of a modication of the electrode structure illustrated in Fig-4j;` y Fig. 'lisa vvertical sectionalfview of a'dlsplacer type switch illustrated inf'fanother' embodiment" ofmy'invention;'andl i I Fig; 8y is a vertical sectional view of-another? form of myinvention similar to `that illustrated inFig.7. Referring to the drawings, Fig. 1 illustrates a mercury switch relay vincluding a coil I I having' 'a central opening, 'a switch envelope I2 disposed ci' the electrodev within the coll opening, 'a' mercury ll I3 within iron circuit including pole sleeves 16 extending into the coil opening Vand defining an air gap' I1. A continuously immersed foot electrode I0 is sealed'through the bottom'wallof the envelope I2, theinnerend of the electrode being in' continuous contact wlththemercury nll Ill. An electrode I9 extends through the upper .end of the envelope ,I2 andis adapted tov be intermittently immersed .by the-mercury illl. The length.` of the electrode I9'may. be varied .with the amount of mercury .within the switch and the diiference betweenvthehigh. and'lowlevels of the mercury. ll, but ordinarily. may Vextend downwardly into the envelope to' a pointfslightly below the low.

I9. may suitably be formed 'offmolybdenumzand the switch envelopellmay be of a hardborosilicatev glass, as these'materials` have substantially equal ,coefficients of thermal expansion which permitsgthe kformation o! a satisfactory' metaltofglass seal.` .Ly 1 g...

A ceramic cup, generally designated 2U, is formed of a highly refractory ceramic material and may be shaped as a hollow cylinder having one end closed by a relatively heavy base 2|, the internal diameter of the cup 20 being substantially greater than the external diameter of the electrode I9. A threaded opening 22 is formed in the base 2l extending outwardly from the inner surface of the cup partially through the base and is adllpind toreceive the loin' andi of the electrode I9; which is provided with lcooperating threads.

The cup 2D is secured to the electrode IS by engaging the threads on the lower end ofg they electrode with those formed within the opening 22. The height of the cup 20`should besuch that when attached, the side Walls willl -extend upwardly around the electrode toapoint abovev bhe low level but below the high level of the mercury ll. The exact proportions of the cup; may bevariedas required, butit is. essential. that the base ZLbe iinner'forateand'.ofr sufcient depthy to. adquatelyinsulatethe lower end'oithe electrode L9, from- `the -mercuryfll-,ll

the side' walls of the cup 2li WlLextendupwardlfy,

around` the lower end of4 the electrode I9 in; a manner similar to thatpreviously describedl It willf-befnotedthat the. cup 25. issimilar to the cup 2,, illustr;atel.in;Fig. hand-may, be formedV of similar materials and of similar dimensions, the.; only? essential difference in; structurey being nemanon.ofrthethreanednenine inheemse. It is, of course, immaterialgwhethergornotmer curyseeps-into,:thef-threadedfopening in the-.base @the fon such. seepage,- cannotshort'. circuitthe switch. l l Fig, YEl,,illustratesj a1' modicatiomof; my' device incorporating@ timee dela/ygA wherein. a; footy elec-- trodellarrd aniintermittently immersedfelectrode, 28eme.- sealed through the-:upperend. of the:- en velopei. l2 and terminate atfsubstantially'thesame levelq which tmay suitably? slightlyi` below the love level of the: mercury llf I 3;, Y Althoughbot-h electrodesgareshowmcnveredl with; aminsulatingV slevev .thisis not; an f ahsolute-:requirement, al,-` thoughaimsomerinstanoesxmaytfbegdesirablea The intermittently; immersedrelectrode :is faxially dis'- Dosedtwithin therenvelopei and isi-provided" withr external .threads;28E formed on itsgextremity; lA relatively i largafceramic. cup; 3i is f providewith an axiallse: disposedrupmardlyrexternding internal, bosshaving; a threadedaxial:opening-adapted trreeeverthe .threadedcloweraend iloizthef interimittentlyzsimmersed:electrodeslli The; opening initheeboss \3\2;1is".:enlarged:atziits uppeiendrto orm a :mercuryr cup: 35; extending: anoundintheielowers portionrofl the .f electrodes-2 8 ;'the`;sides`.:of2 the. cup; Iliextendingl upwardlfyfr ttrzaQpointv above the low; level of 4the::mercury,; filli.. A?. mercury.Y metering oriceftzisrprovided ,inthel bottom-.wall otzthe ceramic `cu'p :.3 Libelowgthe ;lo\v;,le'vel .of-rltli'efvmencunyfsiillr; whereby;:an` smallaqu'antityrotimereuryr is.rat;=ialltimes=.i-etained withinathez-cupzsL The footzelectrode 21 extends@downwardlyv parallel and adjacent to the intermittentlylsimmersedl through the mercury metering orifice 33. f .oni the. other hand, the side walls of the cup electrode 28 and into the mercury retained in the cup 3 l.

The side walls of the cup extend upwardly around both electrodes, the height of the walls being varied according to the time delay characteristics required. If the side walls of the cup 3| are extended upwardly to a point above the high mercury level, the switch will be of the slow make, slow break type, fork in such instance the' ci'rlzuil` between thd electronic! 11 ,and 28 cannot be completed until a predetermined amount of mercury has owed into the cup I1,

terminate at a point below the high level of the mercury'iill, the circuit between the electrodes 'will be instantly completed upon energization of the. displacer Il'.V In either event, deenergization vof the displacer causes the outer level of the mercury illl to fall to a level below the lip ofthe. cup: 31 but; the circuit through! the electrades will'not be. inunediatelur'bmleen due-tothe timing action of the mercury metering1 oribel' whidiemtards: theA iiowz on mercury; from' the cup. Whenythef circuit. betweenV the' electrodes in brolienntliev breakA Willy occur between: therme# cnw/,retained within the. cup1v 3 Il andi inl co'ntuct with thefooty electrode 21xV arrdf the; memuryl retainedin: continuous-contanti with. intermittenth@ immersedelectrode; 23: byL the cup 38.- `lil switchihaving thee structur. descmbedrha'sarelatively; liighr current: carrying' capacity,- f'rf in'4 nd instanoefisthef fiowof; current; between? the'- @leedy tnodes: required..tu` pass; through tlevela't'vely small-,.meter'ing;orice:38 mammina-the inmuxmuy immersediiew trodef 28: isaxiallyA disposed Within'L Ul'efenvelope; t'hezneramicrrwn 31h may: beia'ttaehedfto ltlieint'er mittently immerse'dele'ctrode'r 285by erigayin'githe thneadsvZB onztheilowerf end oiftlieelecbrcdefwth the,A threads .i formed in tliei opening in) the* bess al. uns: structure` has: been found? partie-many desirable:A in time.: delay switbhes; as'ith'efreare no fused: orrcem'entedL-joints to* fe'il under' excessive vibration ori'snookp i the donedennesllimmgf 55- -nlceramiecupsi having an opening srfghnyfirger mmmanifs-c 3dr-maybe secured-tothleelectrddefbycompressing.. me spring: salland inserting 'tneassefrmiynftie cup -312 release, thelspringjfis' forced ri-'5lv suimiylfagamsv the ir'mer wane ofthe cupi :fr andser-vesuto rtairitlicup* in position'.A As 'thL frieden engagea;ene orthefsprmgas winrn' walls {oiftlie cupi 1311' Imay `beincreasedby' the oil-a heavier'-s'prirrg;v thistype of structure'xy be employed in conjunction with a relatively heavy electrode cup such as may be employed in a heavy duty switch.

As a modication of the structure shown in Figs. 4 and 5, the transverse disc 34 and spring 36 may be mounted on the lower electrode 23. In this modiiication a ceramic cup 39 is formed as a hollow cylinder having a transverse intermediate wall 42, the diameter of the -cylinder is made substantially equal to the diameter of the disc 34 and may, therefore, be slipped over the upper end of the foot electrode 23 by compressing the spring section 36, which upon release will frictionally engage the inner walls of the cup 39. The walls of the cup extend upwardly above the intermediate partition 42 and around the electrode I9 to form a mercury cup, designated 44.

Another method of attaching an electrode cup is illustrated in Fig. 7, wherein glass is used to bond the cup to the electrode. In this modiiication, a ceramic cup 46 similar to the cup described in connection with Fig. 1 is provided with an opening 41 extending outwardlyfpartially through the base of the cup, the diameter of the opening being substantially equal to the diameter of the electrode I9. The cup 46 is attached to the electrode I9 by depositing a thin lm of molten glass 49 on the end of the electrode and inserting the electrode into the opening formed in the base of the cup 46 while the glass is still in a fiowable condition. 'I'he glass fuses to both the ceramic material and to the electrode but will form what would ordinarily constitute an unsatisfactory bond, in that the glass will check and crack unless the coefficients of thermal expansion of the electrode, the glass, and the ceramic material are substantially equal. I have found that this checking and cracking does not greatly weaken the bond of the glass to the metal-or to the ceramic material and that it is, therefore, immaterial whether or not checking or cracking of the glass occurs; for, in my structure the switch cannot be short circuited by mercury seeping through the cracks formed in the glass.

'I'his type of cup may also be mounted on the foot electrode, as shown in Fig. 8 wherein a ceramic cup 49 is provided with an opening 52 extending inwardly partially through the base of the cup to receive the upper end of the foot electrode 23. A thin film of molten glass 53 may be deposited on the upper end of the electrode 23 and sealed to the cup in a manner previously described. Side walls I of the cup 49 extend upwardly and surround the lower end of the electrode I9 thereby forming a cup adapted to retain a small quantity of mercury in continuous contact with the electrode.

It should be noted that in all forms of the invention the means for attaching the cup to the electrode is such that the cup is rigidly supported on the electrode and yet mercury leakage past the attaching means can do no harm, and specilcally cannot short circuit the switch.

To comply with section 4888 of the revised statutes, I have described certain specific embodiments of my invention in detail, but as modications may be made without departing from the true spirit and scope, I do not limit myself to the particular details disclosed except as defined in the appended claims.

I claim:

1. In a mercury switch, a switch envelope, a mercury fill, electrode means for the mercury fill including an electrode sealed through the upper portion of the envelope and extending downwardly therein, a pocket member of refractory clay-type ceramic carried at the lower end of said electrode and having side and bottom walls forming a pocket for mercury, said pocket communicating with the space outside of said walls and within the envelope for the flow,

of mercury upon operation of the switch, and means for causing the mercury to ow into and from said pocket; said electrode extending downwardly into a recess in said bottom wall and iitting therein with the side walls of the electrode and the adjacent side walls of the recess approximately parallel, and fusible vitreous means in the form of a thin film surrounding the electrode and intimately engaging said approximately parallel wall surfaces whereby the pocket member will be held fast and supported by the electrode in spite of substantial differences of expansion between the pocket member and the electrode.

2. In a mercury switch, a switch envelope, a mercury fill, electrode means for the mercury flll including an electrode sealed through the upper portion of the envelope and extending downwardly therein, a pocket member of refractory material carried at the lower end of said electrode and supported solely by said electrode and having side and bottom walls forming a pocket for mercury, said pocket communicating with the space outside of said walls and within the envelope for the flow of mercury upon operation of the switch, and means for causing the mercury to fiow into and from said pocket; said electrode extending downwardly through said pocket and having an end portion fitting into a recess in said bottom wall of smaller internal diameter than the pocket and held therein in spite of substantial differences of expansion between the pocket member and the electrode, said recess being closed at its bottom end by the insulating material whereby a mercury-tight seal between the electrode and the insulating material is immaterial.

i CARL H. LARSON. 

